1. Field of the Invention
The present invention relates to a case of a condenser microphone, and more particularly, to a method of forming a sound hole in a case of a condenser microphone that prevents foreign substances from entering the case to improve reliability and the condenser microphone case.
2. Description of the Related Art
Generally, condenser microphones widely used for mobile communication terminals and audio devices are classified into a condenser microphone for an electromagnetic interference (EMI), a ceramic condenser microphone, a micro-electric mechanical system (MEMS) condenser microphone, and a digital condenser microphone according to structures and characteristics of the condenser microphones. Such a condenser microphone includes a metal case, which fixes internal components to one assembly to improve acoustic characteristics.
As shown in FIG. 1, a general condenser microphone case 10 has one or a plurality of sound holes 10a for introducing external sound waves. Although the plurality of sound holes 10a is defined in a cylindrical case 10 in FIG. 1, one or a plurality of sound holes may be defined in a rectangular parallelepiped case.
As the demands of the customers increases now, products that are normally operable at worst environment conditions are required. For this, reliability of the products is further required. In case of a condenser microphone, the fact that foreign substances are introduced into the inside thereof through sound holes defined in a case is the main reason for reliability reduction. To solve this limitation, nonwoven fabrics may be added to the inside or outside of the sound holes. In case where the nonwoven fabrics are used, there are limitations that a manufacturing process for attaching the nonwoven fabrics is added, as well as, foreign substances adhere to the nonwoven fabrics to reduce the reliability.
Thus, each of the sound holes defined in the case may increase in size to prevent the foreign substances from being introduced. However, in a typical sound hole forming process, since the sound hole may be limited in size due to processing limitations, it is difficult to prevent the foreign substances from being introduced.